A Novel Quantitative Assessment Method of Disease Activity in Susac's Syndrome Based on Ultra-Wide Field Imaging

Purpose Susac's syndrome (ScS) is a rare, potentially life-threatening auto-immune disease. Ophthalmic imaging can depict characteristic branch retinal arteriolar occlusions (BRAO) and arterial wall hyperfluorescences that form one of the three diagnostic pillars of this condition. We aim to demonstrate that ophthalmological ultrawide-field (UWF) imaging allows for a qualitative and quantitative assessment in ScS, with application in diagnostics, monitoring of treatment response, and titration of therapy. Methods In seven ScS patients (female:male = 2:5), with a median age of 36 years, range 18 to 57 years, serial ultrawide-field fluoresceine angiography (UWF-FA) studies were performed, with adjunctive wide-field optical coherence tomography angiography analyses (WF-OCTA) in five patients. Mean follow-up was 12.5 months, range 1 to 46 months. Results In all seven patients, BRAO and arterial wall hyperfluorescences were present in UWF-FA and calculated as a quantitative score of disease activity in fluorescein angiography (DA-FA) during follow-up visits. Treatment response was accessible in follow-up imaging as partial reperfusion of retinal vessels, resolution of arterial wall hyperfluorescences and consequently, in reduction of DA-FA score. While qualitative analysis of WF-OCTA provided further information about retinal micro-perfusion, quantitative analysis did not demonstrate a vectored treatment response as it was accessible in FA. Conclusion DA-FA score, as a comprehensive disease activity parameter in ScS has potential to facilitate optimal communication between subspecialties and thereby treatment success.